Manufacture of glassine and greaseproof papers



United States Patent-- Hamilton, Pelllam Manor,'N. Y., assignors, by mesne ligaments, to Rlegel Paper Corporation, New York,

N. a corporation of Delaware No Drawing. 'ApplleatlonMnreh 1954, t SerlalNo. 415,969

7 Claims. '(Cl. 92 -20) The invention relates to the manufacture of glassine and'greaseproof papers, etc. and includes an improved method of manufacture and a novel paper made thereby. Accordingto the invention, screenings, which are nor- I mally rejectedin the screening operations following cooking of pulps suitable for the manufacture of glassine and greaseproof' papers, are subjected to a treatment in which the fibers of the fiber bundles thereof are separated by a relatively gentle curling and twisting operation whereby such separation is elfected with no substantial loss of pentosans and hemicellulose and without substantial mutilation of the fiber structure. During this treatment,

.some of the bark and extraneous dirt are removed. The

resulting pulp is then further cleaned by treatment in a .suitable centrifugal type cleaner and is then subjected to contain considerable amounts of pentosans and hemicellulose. Both the long fiber characteristic and the high hemicellulose characteristic are of substantial importance in a pulp from which glassine and greaseproof papers are to 'be made. It is believed that the bundle formed during the cooking operation protects the cellulose of the fibers, whereby it is not degraded to the extent normal in cooking operations. Furthermore the bundle formed during cooking prevents dissipation of the hemicellulose thereof and prevents loss into the cooking liquor.

According to a specific embodiment of the invention, the screenings from the screening operations following the cooking of anormal'sulphite pulp are subjected to curlation, that is, they are subjected to treatment by a machine of the type disclosed in the aforementioned Coghill Patent 2,622,490. During this treatment thereof the fiber bundles are broken up gently by a curling and twisting action and the fibers thus separated. During this treatment the pentosans and hemicellulose are not lost nor are the fibers mutilated to shorter length. Hence the fiber length which is so beneficial for glassine and greaseproof papers is maintained as are the presence of the pentosans and hemicellulose. Also during this treatment, some of the bark, extraneous dirt and shives from the screenings are removed.

Following the curlation treatment, the so treated sulphite pulp screenings are run through additional cleaning equipment of the centrifugal type, for example, a Centricleaner manufactured by Bauer Brothers, in order to remove any trace of dirt or bark which would be harmful to both the appearance and greaseproof properties of made into glassine or greaseproof papen Furthermore the resulting refined and hydrated pulp can, if desired, be

' blended with normal or regular pulp from which glassine and greaseproof papers arenormally made, the composite, however, being made up substantially of the pulp refined from the screenings.

Heretofore glassine and greaseproof papers have been made primarily from sulphite pulp cooked by the so- .called Mitscherlich process or by an indirect cooking process, orin some instances by a process in which the cooking cycle is lengthened timewise but the amount of cooking chemicals are reduced. The aim has been to preserve as much as possible of the pentosans and hemicellulose inthe pulp in order to give the pulp the-hydrating qualities "required for the making of glassine and g'reaseproof paper. The-cooking methods heretofore em- .ployed have always been rather expensive and have hence resulted in a pulp which has been sold at a premium over regular sulphite pulps. Additionally, while, as indicated, the effort has been made to retain as much as possible of the pentosans and hemicellulose in the. pulps, there has in fact been a substantial loss thereof in the cooking process.

After cooking the pulp is screened. During such screening operations as much as 15% or more of the pulp has been rejected. Normally the rejected screenings have been considered as a waste product and sold at a small fraction of the price obtained for the regular prime sulphite pulp. In certain mills producing newsprint, these normally rejected screenings are run through what has come to be known as a curlating machine, which is fully disclosed in Coghill Patent, 2,622,490, and then been added to the furnish in small quantities.

The present invention is based on the discovery that the screenings normally rejected in the screening opera- .tions following cooking of pulps, and particularly sulglassine and greaseproof papers. During this further cleaning operation, the long fiber length is maintained as is the high pentosan and hemicellulose content.

The thus treated pulp product is then subjected to heating, refining and hydrating in much the same manner as is conventional sulphite pul-p prior to making glassine or greaseproof paper therefrom. This type of treatment is adapted to refine and hydrate with a minimum of cutting and hence with a minimum of fiber mutilation. If desired, the screenings pulp may be admixed or blended before or after such beating, refining and hydrating treatment with normal sulphite pulp or other pulps useful in making glassine and greaseproof papers. Furthermore it may be bleached, if desired, prior to such beating, refining and hydrating treatment. The bleaching operation em-' at substantially higher speed. Whilethe normal or regular sulphite pulp is normally run on the paper machine at a freeness of from cc. down to 30 cc., usually closer to 30 cc. (the method of determining freeness is the modified Canadian standard method) the sulphite screenings pulp treated in the manner set forth above'or an admixture or blend'thereof with other conventional pulps that may be employed for glassine and greaseproof papers may be run on the paper machine at a considerably higher freeness, e. g., up to about cc., and still permit the production of paper therefrom having excellent greaseresistant qualities. Hence the permissibility of higher paper machine speeds for the production of glassine and greaseproof paper therefrom.

. Patented-May 21, 1957 In addition to the economies that may be effected, as

greater strength than are such papers made from a pulp consisting wholly or substantially of normal or regular sulphite pulp. Hence the new product will possess higher tear, Mullen, tensile strength and stretch characteristics.

As indicated, admixtures of the screenings pulp and normal or regular pulps conventionally used in the manufacture of glassine and greaseproof papers may be employed. Such admixtures or blends should be made up, however, substantially of the screenings pulp. It is further contemplated that the screenings from the screening operations performed in the manufacture of pulps suitable for use in glassine and greaseproof papers other than sulphite, e. g. kraft, may be treated in' the manner set forth above specifically in connection with the treatment of sulphite pulp screenings. Such other so-treated pulp screenings may be blended with the treated sulphite pulp screenings for the manufacture of glassine and greaseproof papers according to this invention. In all instances, however, the most substantial portion of the pulp employed in making the glassine and greaseproof papers should be screenings pulp treated as set forth in detail above.

We claim:

1. A method of producing greaseproof and glassine papers which comprises subjecting the screenings from a cooked pulp screening operation to a gentle curling and twisting treatment to separate substantially completely the fibers thereof without removing therefrom any substantial amounts of pentosans and hemicellulose and without substantial mutilation of the fibers, subjecting said screenings to refining and hydration without substantial cutting of the fibers thereoffiand forming the paper from the resulting refined and hydrated pulp.

2. A method of producing greaseproof and glassine.

papers which comprises subjecting the screenings from a. cooked pulp screening operation to a gentle curling and twisting treatment to separate substantially completely the fibers thereof without removing therefrom any sub to a gentle curling and twisting treatment to separate substantially completely the fibers thereof without removing therefrom any substantial .amounts of pentosans and hemicellulose and without substantial mutilation of the fibers, subjecting said screenings to refining and hydration without substantial cutting of the fibers thereof, and forming the paper from the resulting refined and bydrated pulp.

4. A method of producing greaseproof and glassine paper which comprises subjecting sulphite pulp screenings to a gentle curling and twisting treatment to separate sub stantially completely the fibers thereof without removing therefrom any substantial amount of pentosans and hemicellulose and without substantial mutilation of the fibers, subjecting said screenings to refining and hydration without substantial cutting of the fibers thereof, said refining and hydration including beating said screenings only to a substantially higher freeness than normal glassine freeness, and forming the paper from the resulting refined and hydrated pulp. 1

5.-A method of producing greaseproof and glassine papers which comprises subjecting the screeningsfrom a cooked pulp screening operation to a gentle curling and twisting treatment to separate substantially completely the fibers thereof without removing therefromany substantial amounts of pentosans and hemicellulose and'without substantial mutilation of the fibers, cleaning said screenings, admixing said screenings with a substantial amount of chemical pulp from which glassine and greaseproof papers are normally made, the amount of said screenings in. said admixture constituting a substantial portion thereof, subjecting said admixture to refining and hydration without substantial cutting of the fibers therestantial amounts of pentosans and hemicellulose and without substantial mutilation of the fibers, cleaning said screenings, admixing said screenings with a substantial amount of chemical pulp from said glassine and greaseproof papers are normally made, theamount of-said screenings in said admixture constituting a substantial portion thereof, subjecting said admixture to refining and hydration without substantial cutting of the fibers thereof, said refining and hydration including beating said.

screenings only to a substantially higher freeness than normal glassine freeness, and forming the paper from the resulting refined and hydrated pulp. 4

7. A method according to claim 6 in which the screenings are sulphite pulp screenings.

References Cited the file of this patent UNITED STATES PATENTS I 1,921,540 Richter Aug/8, 1933 2,566,130 Karlson Aug. 28, 1951 2,660,097 Hill Nov. 27, 1953 Manufacture of Pulp and Paper, 3rd ed., vol. V, sec. 6,

pp. 23 and'24, pub. by McGraw-Hill, N. Y. (1939). 

1. A METHOD OF PRODUCING GREASEPROOF AND GLASSINE PAPERS WHICH COMPRISES SUBJECTING THE SCREENINGS FROM A COOKED PULP SCREENING OPERATION TO A GENTLE CURLING AND TWISTING TREATMENT TO SEPARATE SUBSTANTIALLY COMPLETELY THE FIBERS THEREOF WITHOUT REMOVING THEREFROM ANY SUBSTANTIAL AMOUNTS OF PENTOSANS AND HEMICELLULOSE AND WITHOUT SUBSTANTIAL MUTILATION OF THE FIBERS, SUBJECTING SAID SCREENINGS TO REFINING AND HYDRATION WITHOUT SUBSTANTIAL CUTTING OF THE FIBERS THEREOF, AND FORMING THE PAPER FROM THE RESULTING REFINED AND HYDRATED PULP. 